Epidemiology of Mumps Let’s move on now to mumps…

Outline Clinical Characteristics Epidemiology of mumps Multistate Outbreak, 2006 Vaccine recommendations Challenges

Mumps Acute viral illness Parotitis and orchitis described by Hippocrates in 5th century B.C. Viral etiology described by Johnson and Goodpasture in 1934 Frequent cause of outbreaks among military personnel in prevaccine era Like measles, mumps is an acute viral illness. Hippocrates was the first to describe the clinical picture of mumps in the 5th century BC. In 1934, Johnson and Goodpasture identified the etiologic agent of mumps as a virus. Although mumps was generally thought of as a disease of childhood, it was also a frequent cause of outbreaks among military personnel in the pre-vaccine era. During WWI, only influenza and gonorrhea were more common causes of hospitalization. Outbreaks are still occurring among military personnel. The last one I’m aware of was on board a ship in the western Pacific in 1992.

Mumps Virus Paramyxovirus RNA virus One antigenic type Rapidly inactivated by chemical agents, heat and ultraviolet light Mumps is a paramyxovirus and is related to parainfluenza, measles and RSV. It is a single-stranded RNA virus with only one serotype. It is rapidly inactivated by formalin, ether, chloroform, heat and UV light.

Mumps Clinical Features Incubation period 14 - 18 days Nonspecific prodrome of low-grade fever, headache, malaise, myalgias Parotitis in 30% - 40% Up to 20% of infections asymptomatic May present as lower respiratory illness, particularly in preschool-aged children Mumps is generally a mild disease but may be severe with some unpleasant consequences. The virus has a predeliction for glandular tissues (e.g. parotid glands, ovaries, testes, pancreas) and nerve tissue. It has a 14-18 day incubation period and typically begins with a prodrome of nonspecific symptoms including low grade fever, headache, malaise and myalgias. The typical swollen parotid glands (either unilateral or bilateral) occurs in 30-40% of cases. Up to 20% of infections are asymptomatic while 40-50% of patients may have respiratory symptoms, particularly children younger than 5 years of age who may develop lower respiratory illnesses.

Parotitis initially may be unilateral, with swelling of the other gland 2-3 days later. The swelling usually peaks and resolves within about 7-10 days. Although this looks alarming, long term sequelae of mumps parotitis are rare. However, serious complications of mumps can occur without evidence of parotitis.

Mumps Complications CNS involvement 15% of clinical cases Orchitis Pancreatitis Deafness Death 15% of clinical cases 20% - 50% in post- pubertal males 2% - 5% 1 / 20,000 1 - 3 / 10,000 Symptomatic meningitis occurs in up to 15% of patients, usually resolving without sequelae in 3-10 days. Adults are at higher risk for this than children, and males at higher risk than females. Testicular inflammation occurs in up to 50% of postpubertal males. About half of these patients are left with some degree of testicular atrophy but sterility is rare. Pancreatitis only occurs in about 2-5% of patients. No causal relationship between mumps and diabetes has been conclusively demonstrated. Deafness caused by mumps is rare and is usually unilateral. Death is also rare with an average of 1 death from mumps per year from 1996-2000.

Mumps Epidemiology Reservoir Human Transmission Respiratory drop nuclei Subclinical infections may transmit Temporal pattern Peak in late winter and spring Communicability Three days before to four days after onset of active disease Humans are the only natural host for the mumps virus. The virus is transmitted via direct contact (such as saliva or infected droplets on surfaces) or by respiratory droplets and enters through the nose and mouth. Asymptomatic or nonclassical infections can also transmit the virus. Mumps peaks in late winter and spring but can occur year round. Patients are communicable 3 days before to 4 days after the onset of active disease.

Mumps – United States, 1968- 2005* Mumps became a nationally reportable disease in 1968. Since the live attenuated mumps vaccine was licensed in 1967, there has been more than a 99% decline in the annual incidence of mumps. *2005 provisional data

Mumps – United States, 1980- 2005* 2-dose schedule … a 2-dose schedule of MMR was introduced in 1989. This likely has played a part in the continuing decline of mumps and the absence of large mumps outbreaks in recent years. *2005 provisional data

U.S. Mumps Cases 2005 – 265 cases 2004 – 258 cases 2002 – 270 cases 2010 Health Objective is to eliminate indigenous mumps by 2010

Mumps Vaccine Composition Live virus (Jeryl Lynn strain) Efficacy 95% (Range, 90% - 97%) Duration of Immunity Lifelong Schedule 2 Doses (as MMR) Should be administered with measles and rubella (MMR) As with measles, the mumps vaccine produces an inapparent or mild noncommunicable infection. A single dose has a clinical efficacy of about 95%. The duration of immunity is thought to be more than 25 years, and is probably life-long in most people. The schedule calls for a single dose of mumps vaccine. However, since measles is recommended as a 2-dose series and we now use the combined MMR, children will be getting 2 doses of mumps vaccine as well. There is not much data on the immune response to the mumps and rubella components from a second dose of MMR. However, most persons who do not respond to the first dose of the mumps or rubella components would be expected to respond to the second dose.

Mumps Vaccine (MMR) Indications All infants >12 months of age Susceptible adolescents and adults without documented evidence of immunity As we discussed with measles, all infants should get one dose of MMR on or after their first birthdays followed by a second dose at least 4 weeks later but usually around 4-6 years of age. Susceptible adolescents and adult without documented evidence of immunity should also have at least 1 dose of a mumps-containing vaccine.

Measles-Mumps-Rubella Vaccine 12 months is the recommended and minimum age MMR given before 12 months should not be counted as a valid dose Revaccinate at >12 months of age 12 months is the minimum recommended age for MMR. MMR given before 12 months of age should not be counted as a valid dose. Sometimes, children as young as 6 months of age may be given MMR as an outbreak control measure if cases are occurring in children less than 12 months of age. However, these and any other children given MMR prior to their first birthdays should be revaccinated with 2 doses of MMR, the first of which should be administered when the child is at least 12 months of age and with at least a 4-week interval after the invalid dose.

Second Dose Recommendations First dose of MMR at 12-15 months Second dose of MMR at 4-6 years Second dose may be given any time >4 weeks after the first dose The second dose is recommended at school entry at 4-6 months of age but may be given as soon as 4 weeks after the first dose. Children who have already received 2 doses of MMR at least 4 weeks apart, with the first dose administered no earlier than the first birthday, do not need an additional dose when they enter school, that is unless mandated by the states or schools.

Second Dose of MMR Vaccine Intended to produce immunity in persons who failed to respond to the first dose (primary vaccine failure) May boost antibody titers in some persons The second dose of MMR is recommended to produce immunity in those 2-5% who failed to respond the first dose. It’s not technically a booster dose, although the second dose may also boost antibody titers in some of those who did respond to the first dose.

However High MMR vaccine coverage levels and vaccine effectiveness likely prevented thousands of additional mumps cases (9 out of 10 exposures that may have resulted in infection in 2 dose vaccinees prevented) Incidence relatively low Disease may be modified Complications and hospitalizations?